(a) Field of the Invention
The present invention relates to a direct current (“DC”)-DC converter including a gate-on voltage/light emitting diode (“LED”) driving voltage generator, and a liquid crystal display (“LCD”) device having the gate-on voltage/light emitting diode (“LED”) driving voltage generator. More particularly, the present invention relates to a DC-DC converter including a gate-on voltage/LED driving voltage generator which provides a driving voltage for an LED and a gate-on voltage driving a gate line, and an LCD device having the gate-on voltage/LED driving voltage generator.
Further, the present invention relates to an aging test apparatus of the LCD device and a method thereof. More specifically, the present invention relates to an aging test apparatus of the LCD device capable of performing an aging test according to a backlight unit of the LCD device, and a method of testing the LCD device using the aging test apparatus.
(b) Description of the Related Art
Generally, LCD devices have been widely used in a broad range of applications due to the characteristics such as light-weight structure, slim profile, low power-consumption, etc. The LCD devices display an image by applying an electric field to a liquid crystal material which has an anisotropic dielectric constant and is disposed between two substrates and adjusting an amount of light which is transmitted to the substrates by controlling the strength of the electric field.
The LCD device includes an LCD panel, a panel driver driving the LCD panel, and a DC-DC converter supplying a driving voltage to the panel driver. Since the LCD panel is a non-light emitting element which may not emit light by itself, the LCDs need a backlight unit supplying light to the LCD panel.
LEDs used as a backlight unit have a long lifespan and fast lighting speeds compared to cold cathode fluorescent lamps (“CCFLs”), etc. and the characteristics of low power-consumption and strong impact resistance. Further, the LEDs have the advantages of miniaturization and light-weight structure.
The LCD devices using the LEDs as a backlight unit must have an additional driving circuit which supplies a driving voltage to the LEDs. The driving circuit which drives the LEDs is separately formed in a DC-DC converter or on a circuit substrate. Accordingly, a further driving circuit which drives the LEDs is necessary, and thus raises costs of the LCDs.
The LCDs take an aging test after a final manufacturing process. Herein, the aging test is a process which puts the LCDs within an aging test driving apparatus, tests properties and reliability of the LCDs while varying temperature and humidity, and stabilizes performance of the LCDs.
Recently, the aging test further includes a high voltage stress (“HVS”) driving method which applies a driving voltage higher than a normal driving voltage to the LCDs. The HVS driving method applies to the LCDs a voltage higher than a plurality of voltages (e.g. a driving voltage, an analog driving voltage, a turn-on/turn-off voltage of a thin film transistor (“TFT”), an inverter driving voltage) necessary for driving the LCDs, and gives stress to the LCDs. The HVS driving method may improve the ability of detecting line defects of the LCDs which may open a circuit according to a voltage level applied by the HVS driving method. Further, the HVS driving method may remarkably reduce an aging time and improve productivity of the LCDs.
The HVS driving method needs a high voltage stress for inverter (“HVI”) power board for driving an HVS power board and a lamp. However, when using the LEDs as the backlight unit for the LCDs, an HVS driving method for the LEDs is needed.